Due to the high costs of raw materials needed to produce synthetic high strength ropes such as ropes made from state of the art synthetic materials including UHMWPE and others, it is important to increase the both the longevity as well as the strength that can be obtained from synthetic high strength ropes for a given amount of material. In the case of increased longevity, the increase in longevity is important in order to reduce replacement costs. Additionally, the increase in longevity can permit use of lowered diameter and thus lighter and less expensive to deploy ropes as in the present state of the art larger than necessary initial diameters are selected in order to provide for a minimum desired longevity of the rope due to anticipated rates of decrease in rope strength and ultimate longevity. In the case of increased strength, the increase in strength is important both to decrease costs of raw materials and production process, costs of rigging equipment needed to carry, lift, stabilize and stably float and/or otherwise sustain and support the weight of the ropes, as well to decrease drag in water and drag in air of such ropes. In the environment of winches, drums and traction winches, i.e. powered blocks, it is especially important to make such ropes more readily usable on such powered blocks. Furthermore, it is important to increase the life expectancy of such ropes in order to obtain the greatest economic advantage from a given investment in any such rope.
While attempts and methods of adhering a steel wire rope's strength member to a sheath surrounding a steel strength member have failed in increasing the steel wire ropes strength, and actually reduce the steel wire rope's strength for a given diameter (a rope's strength necessarily measured in relation to its diameter) such attempts and methods have succeeding in increasing the longevity of certain steel wire ropes. However, in the case of ropes formed with synthetic and/or mainly synthetic strength members, all known attempts to increase the strength and/or the longevity of synthetic ropes by adhering a sheath surrounding a strength member to the synthetic and/or mainly synthetic strength member have failed to increase either the strength of the rope or its longevity, and in fact do the opposite. That is, known methods of adhering a synthetic rope's strength member to a sheath surrounding such strength member actually decrease both the strength and longevity of the ropes. For this reason, such known constructions increase not only the expense of the rope, but also its diameter and thus associated drags in for example water, as well as its weight and thus associated costs for structures affixing, floating, sustaining or otherwise supporting such ropes. As a consequence, it is contrary to the trend in the industry and against the state of the art to adhere to a synthetic rope's strength member a sheath surrounding such strength member.
As another consequence, it is accurate to state that it is contrary to the trend in the industry and against the state of the art to actually improve a rope's strength by adhering a sheath to the ropes strength member, especially by adhering a sheath to a synthetic and/or mainly synthetic ropes synthetic and/or mainly synthetic strength member, and that such result would be surprising to those skilled in the art.
In the present state of the art, when forming high strength synthetic strength members for use in forming a high strength rope, the strongest synthetic fiber available at a certain price point and suitable for a certain environment of intended deployment is used. It is well known that synthetic high strength ropes have a drawback of being very expensive. Furthermore, synthetic high strength ropes are prone to a much more rapid rate of degradation than natural, e.g. wire ropes, and are quicker to experience abrasion induced failure when used on powered blocks, whether in protected environments or in high temperature and abrasive environments, as opposed to when such synthetic high strength ropes are used in static applications. However, due to their relatively light weights and also due to their relative low diameters for a given strength, and also due to their ability to not rust or oxidize in air and humid environments at an appreciable rate compared to metal fibre ropes, state of the art high strength synthetic ropes, such as ropes made from Vectran®, Zylon® (i.e. PBO), Carbon fibers, Aramids and the like are highly desirable in many applications where light weights and minimal diameters are desired in order to minimize structural loads, to enhance aesthetic appearance such as in pleasure yachting, to minimize the costs of structures to which the ropes affix, and also where low drags are desired such as in towed applications and mooring applications, the relatively low diameters of such synthetic high strength ropes providing for lowered drags compared to other ropes. The present state of the art and the current trend in the industry is that such ropes either do not include a sheath about their synthetic strength member, or that if they do include a sheath that no attempt is made and no construction is provided to adhere the sheath and the strength member to one another. This is because, as mentioned above, known constructions and methods for adhering a synthetic strength member to a sheath surrounding such strength member actually decrease the strength of as well as decrease the longevity of known synthetic ropes, including synthetic ropes for use with powered blocks.
Ropes having sheaths such as plastic sheaths surrounding a strength member, and ropes having synthetic barriers including adhesives and thermoplastics between a strength member and a sheath have failed to be successfully used with powered blocks, whether such ropes are synthetic or natural ropes, and the present state of the art and the current trend in the industry is that natural as well as synthetic strength members used with powered blocks have no such type of sheath, as the cost of forming such sheaths has not been proved to be of benefit. It is understood in the industry that a sheath is not a primary strength bearing unit of a rope, whether a natural or a synthetic rope, but rather that a strength member is the primary strength bearing unit forming a rope. Nonetheless, due to the advantages of lightness of weight that high strength synthetic strength member ropes offer, attempts continue to be made to successfully deploy into industry on a wide scale high strength synthetic strength member ropes for use with powered blocks, such attempts including forming a sheath formed of braided strands about such high strength synthetic strength members in attempt to increase the longevity and thus reduce the long term investment associated with using high strength synthetic ropes. However, the very high costs of such high strength synthetic strength member containing ropes compared to natural high strength ropes, e.g. wire ropes, and the fact that such high strength synthetic strength member containing ropes when used with powered blocks experience rather fast deterioration of their sheaths and ultimately of the synthetic strength members, has resulted in the fact that today only limited market acceptance has been gained for high strength synthetic strength member containing ropes for use with powered blocks. That is, known high strength synthetic strength member containing ropes used with powered blocks are known for rather quickly experiencing abrasion induced failure, and for experiencing a rather rapid strength degradation prior to absolute failure for their cost. Due to the extremely high cost of such ropes, their premature failure and short life spans when used with powered blocks, the adoption of high strength synthetic strength member ropes for use with powered blocks has been limited. For example, the vast majority of the world's trawlers even in highly developed regions continue to use wire rope as trawl warps, despite the great weight and safety concerns caused by such weight when the natural high strength rope is stored on a trawl winch—i.e. vessel instability, it being well known that the weight of such stored wire trawling warps has often been implicated in vessel capsize. Thus, a long felt need continues to exist in the industry for a high strength synthetic strength member containing rope capable of being used with powered blocks that has improved longevity, including improved strength retention over time. Thus also, it can be appreciated that a long felt need continues to exist in the industry for a high strength synthetic strength member containing rope capable of being used with powered blocks that has improved strength.
Published Patent Cooperation Treaty (PCT) International Publication Number WO 2004/020732 A2, International Application Number PCT/IS2003/000025 discloses a cable having a thermoplastic core within a braided synthetic strength member. The cable is a heat stretched cable exhibiting ultra compactness and is useful for high tension powered block applications. In one embodiment, disclosed is a cable wherein the material of the thermoplastic core contacts both the synthetic strength member and a braided synthetic sheath formed about the outside of the strength member. However, this embodiment has failed to be commercially accepted for the reasons taught above, i.e. due to the fact that the strength of the cable is reduced by such construction.
In all embodiments, it is taught that the heat stretching and compacting of the cable is accomplished either by simultaneously heating and stretching with tension the combination of the strength member, the thermoplastic core and a second sheath formed about the thermoplastic core and also contained within the strength member, the purpose of such second sheath being to prevent uncontrolled flow of molten phase of the thermoplastic core during processing of the rope, or by first applying the heat and subsequently applying the tension. This cable has found more commercial acceptance than any other synthetic rope for use with high tension powered blocks, and is the only viable synthetic rope in the known art for use with high tension powered blocks such as trawler winches for purposes such as trawl warps, and this cable and its taught manufacturing processes represent both the state of the art as well as the trend in the industry.
Disclosure
It is an object of the present disclosure to provide for a high strength synthetic strength member containing rope for use with powered blocks that addresses the above stated long felt need in the industry.
It is an object of the present disclosure to provide for a high strength synthetic strength member containing rope capable of being used with powered blocks that exhibits improved strength.
It is another object of the present disclosure to provide for a high strength synthetic strength member containing rope capable of being used with powered blocks that exhibits improved strength retention over time and thus improved longevity.
It is yet another object of the present disclosure to provide for a high strength synthetic strength member containing rope capable of being used with powered blocks that exhibits both improved strength as well as improved strength retention over time and improved longevity.
It is yet another object of the present disclosure to provide for a high strength synthetic strength member containing rope capable of being used with powered blocks and satisfying the above stated objects of the present disclosure where such rope is capable of being used in substitution of steel wire strength member containing ropes for applications including but not limited to trawl warps, anchoring lines, seismic lines, oil derrick anchoring and mooring lines, tow ropes, towing warps, deep sea lowering and lifting ropes, powered block rigged mooring ropes, powered block rigged oil derrick anchoring ropes used with blocks and also with powered blocks, superwides and paravane lines used in seismic surveillance including but not limited to used with towed arrays, yachting ropes, rigging ropes for pleasure craft including but not limited to sail craft, running rigging, powered block rigged anchor ropes, drag lines, climbing ropes, pulling lines and the like.
Disclosed is a method for producing a high strength synthetic strength member containing rope capable of being used with powered blocks where such rope has lighter weight and similar or greater strength than steel wire strength member containing ropes used with powered blocks. Disclosed also is the product resulting from such method. Most broadly, the product includes a synthetic strength member, a first synthetic portion and a second synthetic portion, where the first synthetic portion is enclosed within the strength member and/or mainly is enclosed within the strength member and the second synthetic portion is situated external the strength member and/or mainly is situated external the strength member, at least a portion of the second synthetic portion also being situated internal a sheath formed about the strength member, the first and second synthetic portions having differing elasticity values, the second synthetic portion having greater elasticity than the first synthetic portion. Preferably, the elasticity of the second synthetic portion is in a range of elasticity values as taught herein as useful for an adhesive substance capable of adhering the strength member to the sheath, with a range of elasticity of from twenty percent (20%) to five hundred fifty percent (550%) measured at any temperature, within two (2) degrees Centigrade of zero (0) degrees Centigrade, being preferred, such as preferably at zero degrees Centigrade.
In a most preferred embodiment, an additional synthetic substance is situated and/or mainly situated about and between fibres forming the strength member, the additional synthetic substance capable of being an adhesive substance that adheres one to another various fibres forming the strength member and also preferably has an elasticity that is lesser than the elasticity of the second synthetic portion.
Most broadly, the method for producing the high strength synthetic rope capable of being used with powered blocks is characterized by the steps of:
a) providing a core capable of supporting a hollow strength member and capable of fitting within an internal cavity formed by the hollow strength member, this core forming the first synthetic portion;
b) forming a synthetic strength member about the core;
c) situating about the outside of the strength member a substance capable of being, during at least one of its phases, a substance capable of adhering a substance forming the strength member to a substance forming a sheath, the sheath preferably being a braided sheath formed of strands formed of synthetic fibres; and
d) forming the sheath about the outside of both the strength member and the substance capable of being, during at least one of its phases, a substance capable of adhering the substance forming the strength member to the substance forming the sheath, where the substance capable of adhering the substance forming the strength member to the substance forming the sheath has an elasticity that is greater than the elasticity of the core, and that preferably is in the range of elasticity values as taught herein as useful for an adhesive substance capable of adhering the strength member to the sheath, with a range of elasticity of from twenty percent (20%) to five hundred fifty percent (550%) measured at any temperature, within two (2) degrees Centigrade of zero (0) degrees Centigrade being preferred, such as preferably at zero degrees Centigrade.
The substance capable of being, during at least one of its phases, a substance capable of adhering a substance forming the strength member to a substance forming the sheath, forms the second synthetic portion of the rope of the present disclosure.
Most preferably, the method includes the additional step of including about and between fibres forming the strength member a third synthetic substance where such third synthetic substance is capable of adhering one to another various fibres forming the strength member, such third synthetic substance having an elasticity that is lesser than the elasticity of the second synthetic substance.
Due to the disclosed synthetic rope for use with powered blocks light weight compared to steel wire cable coupled with its improved strength, improved strength retention over time and improved longevity, it possesses the advantages of being more buoyant in water than steel wire cable while also being capable of enduring the rigors of use in any of the mentioned applications of use for a longer duration than steel wire cable.
Another advantage of the disclosed synthetic rope for powered blocks is that it permits dramatically reduced superstructures and associated costs for floating mooring and/or anchor lines needed to anchor oil derricks, especially deep water oil derricks and other floating structures.
Yet another advantage of the disclosed synthetic rope for powered blocks is that due to its increased strength less of the rope is required and thus less weight is required to be stored on for example trawler drums, and thus it lowers the center of buoyancy of trawlers using the disclosed rope for trawl warps thereby improving trawler safety.
Yet another advantage of the disclosed synthetic rope for powered blocks is that due to its increased strength less of the rope is required and thus it has a lowered diameter per application requirement, thereby concurrently reducing drags in water and fuel consumption costs associated with pertinent applications including but not limited to trawl warps, superwides and paravane lines, seismic lines anchor lines, deep water oil derrick mooring and/or anchoring lines, drag lines and others as a result of the increased strength of the disclosed rope.
Yet another advantage of the disclosed synthetic rope for powered blocks is that due to its increased strength less of the rope is required and thus it has a lowered diameter per application requirement, thereby reducing costs to produce and acquire the rope.
Possessing the preceding advantages, the disclosed synthetic rope for powered blocks answers needs long felt in the industry.
It can readily be appreciated that these and other features, objects and advantages are able to be understood or apparent to those of ordinary skill in the art from the following detailed description of the preferred embodiment as illustrated in the various drawing figures.